Method of flame hardening



Sept. 27, 1949. I 5. SMITH 2,482,945

METHOD OF FLAME HARDENING Filed Sept. 25, 1946 2 SheetsSheet' 1 i INVENTOR STEPHEN SMITH ATTO R N EYS Sept. 27, 1949. 5. SMITH METHOD OF FLAME HARDENING Filed Sept. 25, 1946 2 Sheets-Sheet 2 FlG. 3

INVENTOR STEPHf/V 5mm BY 6L4 8M1 -65 0am ATTORNEYS the cold gas being used to cool the products of combustion to the point where their heating effect on the metal above the heating zone is no longer objectionable. The metal ahead of the heating zone is kept at a substantially uniform temperature so that a constant depth of heating and surface temperature is obtained throughout the length of the work piece.

The procedure permits flame hardening to be carried on progressively and at constant speed, achieving a uniform depth of hardness from the bottom to the top of the surface under treatment. A further advantage is that the speed of movement of the heating device may be uniform throughout its path of travel, thereby avoiding the necessity for complicated mechanism necessary if the speed must be increased by successive increments because of excessive preheating of the surface.

The heating may be accomplished by combustion of any suitable combustible gas with oxygen or air, provided the necessary amount of concentrated heat can be applied as desired. Oxyacetylene flames are particularly adapted for the purpose, and these may be provided by employing a suitable torch head having means for supplying and mixing the gases and for discharging the mixture through a plurality of circumferentially disposed orifices. The torch head is' also supplied with a quenching medium such as water or cold gas which is discharged through circumferentially disposed orifices below the heating orifices so as to impinge on the previously heated surface. Above the heating orifices are similar orifices supplied with a relatively large volume of a cooling gas suchas air, jets of which impinge on the surface to be treated and mingle with the products of combustion and with the envelope gases,

'thus maintaining the low temperature of the surface'by preventing preheating thereof and by withdrawing heat transferred through the metal from the heating zone. The volume of cooling gas should be such as to reduce very materially the temperature of the combustion and envelope gases, though the exact temperature is not critical.

The torch head may be mounted in any suitable manner to permit movement thereof at a uniform rate upwardly as the hardening operation progresses. Thus water, if used as a quenching agent, will run downwardly without interfering with the heating.

Referring to Fig. l of the drawing, 2 indicates a fixture having a bore 3 and a ledge 4 which is adapted to support a work piece 5 having a bore or cylindrical surface 6 which is to be hardened by the practice of the invention as described herein. A torch head I is supported on a tubular member 8 for vertical movement in the bore 6, preferably from the bottom upward, as hereinafter described. The lower end of the tubular member 8 is secured to a block 9 which is threadedly connected to a tubular member I!) having a conical end H which fits snugly in a conical seat 12 of a block l3. A threaded nipple I4 is connected to the block l3 and a hose (not shown) may be secured to the nipple and connected with a source of oxygen which flows through the passage l5 in the tubular member 10. A threaded nipple I6, also secured to the block I3, is adapted to be connected by a hose (not shown) to a source of acetylene which flows through the passage I! to a groove 48 and thence through inlets with the oxygen and provides the fuel to maintain the heating jets.

A tubular member ID concentrically surrounds the member 10. One end of the member Hi seats on a ledge in the block 9 and the other end fits against the conical seat 12 of the block 53. The member 10' is secured to the block [3 by a nut 20 which holds the conical end of this member In firmly against the seat 12. A nut 2| surrounds the member Ill and engages the block 9, packing 22 being disposed behind the nut 2| to prevent leakage of quenching medium from passage 23 formed between the members It and in. This passage 23 communicates via a passage 24 (Fig. 2) with a nipple 25 which is adapted to be connected through a hose (not shown) with a source of quenching medium such as water or a cold gas.

Within the tubular member 8 are two concentrio tubes 26 and 21, forming passages 28, 29 and 33. The end of the tube 21 terminates in a threaded nipple 3| which is adapted to be connected through a hose (shown dotted) with a source of air or other cooling gas under pressure. The latter is conducted through the tube 21 to a chamber 32 at the top of the torch head 1, and a plurality of orifices 33 distribute the cooling gas under pressure circumferentially about the torch head in a plurality of jets which impinge upon th cylindrical surface 6.

Directly below the chamber 32 is a chamber 34 which communicates with the passage 29 between the tubes 23 and 21. This passage in turn communicates with the mixing chamber [5, and thus the mixture of combustible and oxidizing gas is delivered to the chamber 34 and distributed through a set of staggered orifices 35 disposed circumferentially about the torch head 1. When ignited, the gaseous mixture forms a plurality of flame jets which impinge upon the cylindrical surface 6 to effect the desired heating thereof. Below the chamber 34 is a third chamber 36 communicating with the passage 28 formed between the tubular member 8 and the concentric tube 26, and this passage 28 communicates with a passage 31 that is connected by a passage 38 with the passage 23, thus affording a supply of quenching medium such as Water to the chamber 36. The water is'distributed through a plurality of circumferentially disposed orifices 4B in the torch head I so that the quenching medium impinges upon the surface 6 below the flame jets. A deflecting shield 6| is removably attached to the fixture 2 by the supporting links 62 and rotatable dogs 63. The quench water falls on the deflecting shield 6i and is directed by a lip 64 to run off at the desired point.

To effect the vertical movement of the torch head 7, the block 9 may be mounted upon any suitable clamping device such as clamps 65 which are rigidly attached to a support 66 fixed to a base 61. This base 61 is supported by a piston rod 68 of a hydraulic cylinder 33 (Fig. 3). A fixed guide 10 maintains the torch head centered in the work piece. Other apparatus capable of moving the torch vertically may be employed.

With the structure illustrated, the torch head 1 can be disposed below the lower edge of the surface 6, the combustible gas may be ignited to produce the flame jets and thereafter the torch head may be raised at a uniform speed through the work piece to be hardened. As the torch head 'I rises, each increment of the surface 6 is subjected successively to the cooling effect of the cooling gases, is then heated rapidly to the critical temperature and immediately thereafter is cooled by the cooling medium to reduce the temperature and eifect the desired hardening of the surface.

The surface 8 above the level of the heating flames is continuously maintained at a relatively low and uniform temperature as the result of the large volume of cooling medium which continuously impinges on and flows upwardly over the surface. 'The hardening results are of uniform character.

Various changes may be made in the details or the operation and in the apparatus employed without departing from the invention or sacrificing the advantages thereof.

I claim:

The method of hardening cylindrical surfaces of a hardenable ferrous alloy which comprises positioning the cylindrical surface in a substantially vertical position, progressively moving jets of relatively cold gaseous medium axially and upwardly of the cylindrical surface and directing them onto the surface to be hardened to precool it to a substantially uniform temperature, pro- 6 gressively directing an annular row of heating flames against the precooled surface closely adjacent the portion of the surface against which the precooling gaseous medium is being directed, the intensity of the flames and the duration of their contact with the precooled surface being suflicient to bring the surface progressivel to its critical temperature, and progressively directing jets of a quenching liquid onto the heated surface immediately beneath the zone of application of the heating flames.

STEPHEN SMITH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 20 2,065,627 Taylor Dec. 29, 1936 2,279,564 Emery et a1 Apr. 14, 1942 2,318,145 Emery et a1. May 4, 1943 2,382,515 Smith Aug. 14, 1945 

